1. Field of the Invention
The present invention relates to a video information transfer processing system, more particularly, it relates to a video information transfer processing system having a color extraction circuit provided with logical circuits, which can carry out a high speed color extraction when the contents of a video memory are processed for transfer from the video memory to a main memory device.
2. Description of the Related Art
For a coloration or sending data to a color printer, for a color figure displayed on a display device, a selective extraction of specific colors is sometimes practiced. This extraction is explained in FIG. 3. FIG. 3 shows examples in which the selected and extracted colors having logical values "0,1,0", "1,0,1", and "1,1,0" corresponding to planes 0 to 2, respectively, in eight colors combined with logical value "1" or "0" for each pixel of the planes 0 to 2 of a video memory. Assuming that the plane 0, the plane 1, and the plane 2 corresponding to the three primary colors red, green, and blue, respectively, the selection of the logical value "0,1,0" results in the extraction of green, the selection of the logical value "1,0,1" results in the extraction of purple, and the selection of the logical value "1,1,0" results in the extraction of yellow.
When the color is extracted as shown in FIG. 3, hitherto, for example, the contents of the three planes were read to determine whether pixels (each shown as a dot) having a certain color in the eight colors were present or not, the color of each dot was recognized by a combination of data from the planes, and the domain of the color was taken out.
According to the above-mentioned conventional processing, in order to extract the specific color, a central processing unit (CPU) had to carry out this process under the command of a software in a video information transfer processing system. This processing was disadvantageous since, in this processing, a general purpose equipment was used, and thus it was difficult to carry out the process at a high speed, and moreover, the CPU was occupied for a long time, which had an adverse effect on the outer processings.
The present invention proposes to solve the above-mentioned problems in the conventional system.